The present invention relates to servo motor operated rotary valves and particularly valves of the type intended for use in controlling flow of fluid in an engine coolant circuit, as for example, valves employed for controlling flow of engine coolant to a cabin heat exchanger or heater core or for controlling flow of coolant to the engine block cooling passages.
Servo motor operated heater core water valves and servo motor operated temperature control valves for engine coolant are desirable inasmuch as an electronic controller may be employed to provide direct control of the fluid flow in real time response to transient conditions in place of static setting of the valve or having the valve only able to respond to changes in the fluid temperature utilizing a temperature responsive valve. However, where an electrically operated servo motor actuator is employed to control cabin heater core water flow or flow of coolant between the engine and the ambient coolant heat exchanger or radiator, provision must be made for the fluid flow to continue in the event of electrical failure or mechanical failure of the servo actuator. This is particularly true for flow of engine coolant to the cabin heater core where the vehicle is being operated in cold climatic conditions in order to ensure survival of the vehicle occupants.
Presently, in production motor vehicles; a rotary type water valve for the heater core has been found to be much superior to a butterfly type water valve for providing accurate modulation of the flow to the heater core or in the regulation of coolant within the engine for purposes of optimizing fuel economy and emissions. However, modulating rotary water valves for the vehicle cabin heater core require a low cost servo actuator which has a minimum volume to facilitate installation of the motorized valve in the vehicle temperature control system which is commonly mounted on the cabin front bulkhead or firewall of the engine compartment. In order to provide a reduced size and low cost actuator, a small subfractional horsepower high RPM motor has been employed through a speed reducer or a gear box to drive the rotary valve. However, in the event of failure of the motorized drive or loss of electrical power in such an arrangement with the valve in the closed position, the result is loss of heat to the cabin heat exchanger and an unacceptable risk or threat to the survival of the occupants of the vehicle in cold climate operation and potential loss of coolant flow to the engine.
Therefore, it has been desired to provide a way or means of providing emergency flow of engine coolant in the event of failure of the rotary water valve controlling flow to either the cabin heater or to the engine coolant heat exchanger or radiator in the event of failure of the electrically operated modulating water valve in the closed portions.
The present invention provides a servo motor operated modulating rotary valve assembly, particularly suitable for controlling flow of engine coolant to a heater core or radiator and has a servo motor and speed reducer attached integrally therewith. The valve assembly further has an integrally formed bypass which is operated by an integral electrical actuator, preferably a solenoid, which is spring biased to the normally open condition when the solenoid is de-energized. The present invention thus provides a servo motor driven modulating rotary valve with an integral bypass that is electrically closed upon system start-up and can either be opened on command or in the event of system electrical power failure. Thus, the integral motorized rotary valve of the present invention provides for emergency bypass in the event of malfunction of the rotary valve actuator or power failure with the rotary valve in the closed condition.